Vapor degreasing with solvent distillation and condensation recovery



B. RAND 3,375,177 VAPOR DEGREASING WITH SOLVENT DISTILLATION AND March 26, 1968 CONDENSATION RECOVERY Original Filed May 18, 1964 INVENTOR. 1 EUR 7'0A/ RAND M Mimi...

A T 706M57 United States Patent 3,375,177 VAPOR DEGREASING WITH SOLVENT DISTILLA- TION AND CONDENSATION RECOVERY Burton Rand, Nat-berth, ,Pa., assignor to Autosonics, Inc., Conshohocken, Pa., a corporation of Pennsylvania Continuation of application Ser. No. 368,116, May 18, 1964. This application May 5, 1967, Ser. No. 637,318 Claims. (Cl. 203-39) This invention relates to degreasing apparatus, and in particular, a solvent vapor control system for such apparatus.

This application is a continuation of application Ser. No. 368,116, filed May 18, 1964, now abandoned.

Vapor degreasing apparatus is used for removing oil from metal parts. The metal parts ,are cleaned by the degreasing apparatus, and then may be remachined if necessary, and either stored for future use or put back into service.

Vapor degreasing apparatus usually includes an open topped vessel in which cleaning vapors are generated by boiling a solvent in a heated chamber. The generated vapors rise within the vessel and contact metal parts supported upon a work rest within the vessel. The vapors will dissolve the grease on the metal parts.

The vessel used in the degreasing apparatus is usually open at one end. This is done in order to provide ready access to the interior of the vessel and to allow escape of the generated vapors before they reach explosive proportions. While some degreasing vessels include a work supporting grate mounted therein, others have a conveyor belt or basket disposed in the working vapor zone of the vessel through the open access top.

The necessity of an open access vessel in degreasing apparatushas caused several problems. These include: (1) excessive loss of the solvent rendering the degreasing operation costly; (2) noxious solvent odors emitted from the apparatus; and (3) a toxic hazard to personnel through air pollution.

It is therefore desirable to control the vapors generated by the apparatus before they are expelled into the atmosphere. One proposed solution is to place cold water condensers around the inside walls of the degreaser, or located at one end of the unit, for condensing the generated vapors before they reach the atmosphere. Also, a cold water jacket encircling the degreaser at approximately the vapor line has been proposed. The jacket prevents the metal walls of the degreaser from warming. If the walls are allowed to warm, light solvent vapors are encouraged to rise and escape from the open top.

The above proposals have not been found completely satisfactory. There is a tendency for the lighter vapors gen erated from the solvent to pass the cooling coils and escape to the atmosphere.

Accordingly, it is an object .of this invention to disclose a solvent vapor control for use in degreasing apparatus for condensing a substantial portion of the vapors before they are expelled into the atmosphere.

A further object of this invention is to provide apparatus in a degreaser for suppressing the rising of lighter vapors which cause excessive loss of solvent, complaints from personnel of solvent odor, and a toxic hazard to .personnel through air pollution.

For the purpose of illustrating the invention, there is shown in the drawings a form which is presently preferred; it being understood, however, that this invention .is not limitedto the precise arrangements and instrumentalities shown.

FIGURE 1 is a perspective view of the degreasing apparatus comprising the subject matter ofthe instant invention, with certain portions broken away for purposes of illustration.

3,375,177 Patented Mar. 26, 1968 FIGURE '2 is a fragmentary sectional view taken along a plane through the center of the apparatus shown in FIGURE 1.

FIGURE 3 is an enlarged detailed fragmentary sectional view of the upper left hand portion of the apparatus illustrated in FIGURE 2.

The degreasin apparatus comprising the subject of this invention is generally designated by the numeral 10. The degreaser 10 has an open-topped receptacle 12 including a bottom wall 14 and a plurality of upright side walls 16.

A solvent 18 partially fills the receptacle 12. The solvent 18 is used to remove oil from metal parts. Suitable solvents for such a purpose include trichlorethylene, perchlorethylene, methylene chloride, Chlorothene, and Freon.

Mounted adjacent the bottom wall 14 and immersed within the solvent 18, are a plurality of heating coils 20. The heating coils 20 are adapted to boil the solvent 18 and generate vapors 22. A work support (not shown) may be disposed within the vapors 22. Alternatively, a basket or a conveyor belt carrying metal parts may be run into the receptacle 12 and through the vapors 22. The vapors 22 are adapted to dissolve oil and grease on the metal parts, thus cleaning them.

A plurality of water-carrying coils 24 are supported by the upright walls 16 of the receptacle 12. The coils 24 are adapted to ring the upright walls as shown most clearly in FIGURE 1. The vapors 22 which come in contact with the cooling coils 24 will condense. The con densate is collected in a trough 26 supported by the upright walls 16 beneath the coils 24.

A cold water jacket 28 also encircles the degreaser at approximately the vapor condensing line. The water jacket 28 cools the metal walls of the receptacle 12. If the walls are allowed to warm, light solvent vapors are encouraged to rise and escape from the open top of the receptacle 12.

While I have not shown the complete water circulation system for the coils 24 and jacket 28, it should be understood that the requisite pumps and heat exchanging equipment are conventional and do not form part of the present invention.

While a substantial portion of the vapors are condensed by the coils 24, the lighter vapors, as well as the vapors in the middle of the receptacle usually are not. These lighter vapors are indicated by the numeral 32.

In order to condense the lighter vapors 32 before they reach the atmosphere, I have provided a plurality of finned coils 34, supported by conventional means (not shown), around the upright walls 16 of the receptacle 12. As will be apparent, coils 24 are discrete with respect to coils 34 in that they are not in fluid communication directly or indirectly. The coils 34 are chilled by me chanical refrigeration to temperatures not above 0 F. They are located approximately midway between the water coils 24 and the open end of the receptacle 12.

The coils 34 are connected by conduits 42 and 44 to a compressor and pump unit 30. A refrigerant is pumped through the coils 34 to maintain the coils at a temperature not above 0 F.

While I have found that the refrigeration coils 34 will substantially decrease the escape of solvent to the atmosphere, a further improvement is achieved by :partially enclosing the finned coils 34 in such a manner as to encourage the vapors 32 to flow towards the coils .34. This was achieved by providing a shield 36 in surrounding, but spaced relationship from the refrigerantcarrying coils 34.

An L-shaped hood 37 having a horizontal lip 38 is interposed between the upright walls 16 and the coils 34. The shield 36 is fastened to the L-shaped hood 37 by means of small L-shaped clips 46. The hood 37 is supported by any conventional means on the upright Walls, such as hanging straps. A bleed passage 39 is formed by spacing the shield 36 from the upright walls 16 and the vertical leg of the hood 37.

In operation, the coils 34, shield 36, and horizontal lip 38 of the hood 37, establish a convection path. The air around the coils 34, being cooler than the vapors 32, will leak through the bleed passage 39. The air will be heated by the vapors 32 and rise adjacent the shield 36. The light rising vapors 32 will be entrained in the heated air and sucked into the space between the horizontal lip 38 and the end ofthe shield 36. The vapors 32, when contacted by the coils 34, will condense. The condensate, will drip through the bleed passage 39 and be collected within the condensate trough 26 adjacent the coils 24. Hence, there is a continuous movement of air around the shield 36 and into contact with the coils 34. A convention current is set up by the use of the coils 34, shield 36, and hood 37 to encourage the natural tendency of the vapors 32 to gravitate towards the refrigerant-carrying coils 34.

A dead air space 40 is also provided in the shield 36. The dead air space 40 insulates coil 34 and helps maintain the low temperature of the finned coils.

Comparison tests were run for three different types of operation of the solvent vapor control system previously described. Tests were conducted to ascertain solvent loss and odor emanating from the degreasing unit 10. The degreasing unit It was operated first with the water jacket and condensing coils only. Secondly, the unit was operated with the water jacket, condensing coils, and unshielded refrigerated coils. A final test was run using a water jacket, condensing coils, and shielded refrigerated coils. The runs were for equal durations of time of less than one day. The results are set forth in the following chart:

Type of Operation Solvent Loss Odor 1. Pronounced.

. 75 Tolerable.

. Almost none.

It will be appreciated that more volatile solvents can now be used more economically in my degreasing apparatus. The more volatile solvents boil at lower temperatures, as for example, compared to commonly used trichlorethylene.

The lower the boiling points of the solvents used, the less is the burden on airconditioning equipment within a plant because of the lower temperatures required to operate the degreasers. Surface heat radiation from the receptacle walls is also lessened.

Also, in the normal operation of a conventional degreaser, the presence of water moisture is harmful to many degreasing operations. The refrigerated coil will act as a dehumidifier and reduce the amount of water moisture in the degreaser.

The refrigeration unit within the degreaser can be kept operating 24 hours per day. This will considerably reduce the normal loss of solvent through evaporation even though the degreaser may not be in operating use.

A substantial conservation of cooling water can be effected by the use of my solvent control system. There is no longer any need for a large volume water fiow through the cooling coils 24 and water jacket 28. In fact, the water jacket 28 may be completely eliminated from the equipment.

A timer may be incorporated into the refrigeration system to defrost the finned coils 34 periodically. Accumulated water will drain through the bleed passage 39, into the condensate trough 26, wherein it can be collected and separated from any accumulated solvent.

Although I have mainly described degreasing appa ratus, it should be apparent that my invention can be put to other industrial uses. For example, the unit 10 can be used as a distilling plant. This is particularly true in the distilling of the solvent for removal of contaminants.

The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof, and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification as indicating the scope of the invention.

I claim:

1. Apparatus comprising:

(a) an open-topped receptacle adapted to be partially filled with a volatile solvent,

(b) means adjacent the bottom of said receptacle for containing the solvent to be vaporized,

(c) first condenser means supported by said receptacle above the solvent for condensing vapors generated from said solvent and thereby defining the upper limit of a vapor zone above the solvent,

(d) a discrete second condenser means supported by said receptacle above said first condenser means and substantially below the upper edge of the receptacle for condensing solvent vapors unaffected by said first condenser means, and

(e) said second condenser means being spaced from walls of the receptacle, means defining a convection flow path for solvent vapors between said wall and outer periphery of said second means, and said second condenser means being substantially colder than said first condenser means,

(f) and a condensate collection trough below said condenser means for collecting condensate and preventing condensed moisture for mixing with the solvent,

(g) said second condenser means including at least one refrigerant-carrying coil, a shield for said second condenser means, said shield being hollow, and said second condenser means being between a portion of said shield and a wall of said receptacle.

2. Apparatus comprising: I

(a) an open-topped receptacle adapted to be partially filled with a volatile solvent,

(b) said receptacle including a bottom wall and a plurality of upright walls connected to said bottom wall,

(c) means for controlling the temperature of the solvent so that the solvent vaporizes,

(d) first condenser means supported by said upright receptacle walls for condensing solvent vapors to define the upper limit of a vapor zone,

(e) second condenser means supported by said upright receptacle walls substantially below the upper edge of the receptacle and above said first condenser means for dehumidifying the space in the receptacle above said zone, said second condenser means being substantially colder than said first condenser means with the temperature of said second condenser means being below the freezing temperature of water at atmospheric pressure, said second condenser means being discrete with respect to said first condenser means and thereby being free from any direct or indirect fluid communication with said first condenser means, a condensate collector below said first condenser means, means coupled to said second condenser means for selectively defrosting the same, said first and second condenser means being operable simultaneously,

(f) means defining in conjunction with said second condenser means and upright receptacle walls a convection flow path bringing air from within the receptacle into the space between said upright walls and said second condenser means so that air cooled and dehumidified by said second condenser means may pass downwardly into the space above the vapor zone and below the plane of said second means.

3. A method for condensing solvent vapors generated in an open-topped receptacle before they are discharged into the atmosphere, the method comprising the steps of: (a) using a cooling coil to define a vapor zone immediately above the solvent in said receptacle,

maintaining said receptacle open to the atmosphere thereabove at all times,

(b) generating an air convection current at a temperature substantially colder than the temperature of said zone and located above the plane of said Zone so that a portion of the current is forced to flow in a downward direction, introducing articles to be cleaned into said vapor zone,

() entraining a substantial portion of the solvent vapors not condensed by said cooling coil in said convection current, and

(d) subjecting said entrained vapors and any entrained moisture to contact with a refrigerant-carrying coil adjacent said portion of the convection current and at a temperature substantially lower than the temperature of said cooling coil to cool said portion of the current and condense said last-mentioned vapors,

(e) directing cooled dehumidified air in said current downwardly below the plane of said refrigerantcarrying coil toward said vapor zone, said refrigerant-carrying coil being at a temperature between 0 F. and the freezing temperature of water so that moisture entrained in said current will freeze on the refrigerant-carrying :coil.

4. A method of condensing solvent vapors generated in an open-topped receptacle before they are permitted to discharge into the atmosphere comprising the steps of generating solvent vapors in said receptacle, establishing a vapor zone in said receptacle, introducing articles to be cleaned into said vapor zone, providing a condenser means in said receptacle substantially below the upper edge of the receptacle and at a temperature below the freezing temperature of water and at a temperature substantially below the temperature of said zone, causing solvent vapors and moisture to move downwardly past said condenser means toward said zone, condensing said solvent vapors and moisture on said condenser means with the moisture freezing on said condenser means so that air cooled by said condenser means flows downwardly below the plane of the condenser means, periodically defrosting said condenser means, collecting condensed vapors and any defrosted moisture, and then separating said collected moisture from said condenser vapors so that the condensed vapors may be reused.

5. Apparatus comprising an open-topped receptacle adapted to be partially filled with a volatile solvent, means adjacent the bottom of the receptacle for heating a solvent, first condenser means supported by said receptacle for condensing vapors generated by said heated solvent, second condenser means supported by said receptacle above said first condenser means for condensing solvent vapors unaffected by said first condenser means, said second condenser means including at least one refrigerant-carrying coil within and spaced from said receptacle, and a shield juxtaposed to the inner periphery and the lower portions of said coil, said shield being spaced from said coil and receptacle, said shield being hollow and defining in conjunction with said receptacle a convection flow path therebetween for solvent vapors.

References Cited UNITED STATES PATENTS 1,926,652 9/1933 Rosenfeld 62-234 2,020,335 11/1935 Savage 202- 2,090,192 8/1937 Edhofer et al. 202-170 X 2,650,085 8/1953 Burnett 203-87 X 2,816,065 12/1957 Legler 202-170 3,242,057 3/1966 Talian et al 202-170 X 3,242,933 3/1966 Huff 134-68 X FOREIGN PATENTS 725,802 5/1932 France.

464,063 4/ 1937 Great Britain.

857,151 12/1960 Great Britain.

NORMAN YUDKOFF, Primary Examiner.

F. E. DRUMMOND. Examiner. 

1. APPARATUS COMPRISING: (A) AN OPEN-TOPPED RECETACLE ADAPTED TO BE PARTIALLY FILLED WITH A VOLATILE SOLVENT, (B) MEANS ADJACENT THE BOTTOM OF SAID RECEPTACLE FOR CONTAINING THE SOLVENT TO BE VAPORIZED, (C) FIRST CONDENSER MEANS SUPPORTED BY SAID RECEPTACLE ABOVE THE SOLVENT FOR CONDENSING VAPORS GENERATED FROM SAID SOLVENT AND THEREBY DEFINING THE UPPER LIMIT OF A VAPOR ZONE ABOVE THE SOLVENT, (D) A DISCRETE SECOND CONDENSER MEANS SUPPORTED BY SAID RECEPTACLE ABOVE SAID FIRST CONDENSER MEANS AND SUBSTANTIALLY BELOW THE UPPER EDGE OF THE RECEPTACLE FOR CONDENSING SOLVENT VAPORS UNAFFECTED BY SAID FIRST CONDENSER MEANS, AND (E) SAID SECOND CONDENSER MEANS BEING SPACED FROM WALLS OF THE RECEPTACLE, MEANS DEFINING A CONVECTION FLOW PATH FOR SOLVENT VAPORS BETWEEN SAID WALL AND OUTER PERIPHERY OF SAID SECOND MEANS, AND SAID SECOND CONDENSER MEANS BEING SUBSTANTIALLY COLDER THAN SAID FIRST CONDENSER MEANS, (F) AND A CONDENSATE COLLECTION TROUGH BELOW SAID CONDENSER MEANS FOR COLLECTING CONDENSATE AND PREVENTING CONDENSED MOISTURE FOR MIXING WITH THE SOLVENT, (G) SAID SECOND CONDENSER MEANS INCLUDING AT LEAST ONE REFRIGERANT-CARRYING COIL, A SHIELD FOR SAID SECOND CONDENSER MEANS, SAID SHIELD BEING HOLLOW, AND SAID SECOND CONDENSER MEANS BEING BETWEEN A PORTION OF SAID SHIELD AND A WALL OF SAID RECEPTACLE. 